Sodium or potassium hydrocarbon compound and a crown ether as a catalyst composition for polymerization of conjugated dienes

ABSTRACT

Conjugated dienes are polymerized in hydrocarbon solution by a new catalyst system which gives polymer products of desirable properties. This catalyst system comprises: (1) a sodium or potassium alkyl having 1-10 carbon atoms in which the hydrocarbon portion is a primary, secondary or tertiary alkyl radical, and (2) a crown ether as defined more fully hereinafter. The polymer products are particularly useful in tire compositions.

United States Patent [191 Halasa et al.

SODIUM OR POTASSIUM HYDROCARBON COMPOUND AND A CROWN ETHER AS A CATALYST COMPOSITION FOR POLYMERIZATION OF CONJUGATED DIENES Inventors: Adel F. Halasa, Bath; Tai Chun Cheng, Akron, both of Ohio Assignee: The Firestone Tire & Rubber Company, Akron, Ohio Filed: Feb. 26, 1973 Appl. No.: 335,962

US. Cl. 260/942 M, 260/821, 260/837 260/923, 260/935 R Int. Cl C08d 3/06 Field of Search 260/942 M, 82.1, 83.7

References Cited I UNITED STATES PATENTS House 260/669 [451 Dec. 24, 1974 Mertz-weiller et al. 260/942 M X House 'et al. 260/942 M X Primary Examiner-Joseph L. Schofer Assistant ExaminerMaria S. Tungol [57] ABSTRACT 17 Claims, N0 Drawings .1 SODIUM OR POTASSIUM IIYDROCARBONv COMPOUND AND A CROWN ETIIER AS A CATALYST COMPOSITION FOR POLYMERIZATION OF CONJUGATED DIENES BACKGROUND OF THE INVENTION catalyze the polymerization of dienes with the polymer-,

ization generally conducted in hydrocarbon solvents. Ethers such as tetrahydrofuran, diethyl ether, diglyme, dioxane, etc., have been used in combination with the lithium hydrocarbon to give higher proportions of 1,2 configuration in the resultant polymer structures as well as other desirable properties. However when sodium and potassium hydrocarbon compounds are used with such ethers, the ethers are cleaved by the sodium or potassium compound with the result that the polymers produced are of low molecular weight and very poor yields are obtained.

STATEMENT OF THE INVENTION In accordance with thepresent invention, it has now been found that sodium and potassium hydrocarbon compounds can form complexes with high molecular weightcyclic ethers, known as crown ethers as described more fully hereinafter, and such complexes can be used to catalyze the polymerization of conjugated dienes inahydrocarbon solvent to give high molecular weight polymers having 65-85, preferably 7075 per cent 1,2 configuration with high conversion to polymers having a broader molecular weight distribution than generally obtained with accompanying improved process-ability, and capable of being used in tire compositions to give good wet traction properties, good wearability, etc.

In contrast to the ether cleavage effected by the sodium and potassium compounds with smaller ethers, it is found that the complexes formed by sodium and po tassium alkyl compounds with crown ethers are very stable and are particularly useful for diene polymerizations conducted in hydrocarbon solvents. The crown ether may be added to the hydrocarbon solvent prior to or after the addition of the sodium or potassium hydrocarbon.

It is also found that the catalyst ofthis invention gives much higher molecular weight polymers than obtained with Li alkyl. For example, the crown ether Na or K alkyl catalystsgive 'DSVs of 2-l0 whereas Li alkyl in THF generally gives no higher than about 1 DSV.

It is found that a much smaller proportion of crown ether to metal alkyl needs to be used. For example, it is generally necessary to use about millimoles of tetrahydrofuran per millimole of lithium alkyl whereas less than 0.1 and even as little as 0.01 millimole of crown ether per millimole of Na or K alkyl is satisfactory in the present invention. Moreover, with Li alkyl and the small ethers, temperatures higher than 60 C. must be avoided to prevent cleavage of the ether by the Li alkyl, whereas temperatures as high as 150 C. may be used in the present invention.

The sodium or potassium hydrocarbon compound is used in a proportion of l-l0 millimoles, preferably 27 millimoles per 100 grams of monomer. The crown ether is used in a ratio of 0.01-1.0, preferably 0.0150.5 millimoles per millimole of sodium or potassium hydrocarbon. I

The crown ethers can have various structures. but are characterized by the fact that they have a heterocyclic ring in which there are at least three, preferably at least four oxygen atoms in the heterocyclic structure connected by aliphatic or aromatic divalent hydrocarbon groups, and in each heterocyclic ring there are at least 6, preferably at least 8 carbon atoms, there being at least 2 carbon atoms per oxygen atom and there being no particular advantage in having more than a total of 60 atoms in the heterocyclic structure of the crown ether. Such structures are found to complex very easily with the sodium or potassium hydrocarbon compounds. When an aromatic or cycloaliphatic ring is present there is advantageously a pair of oxygen atoms attached to adjacent (or ortho) carbon atoms in such aromatic or cycloaliphatic ring.

Some of the oxygen atoms in such heterocyclic rings,

preferably no more than 50 percent, may be replaced byamino nitrogen radicals or sulfur atoms, which also contribute complexing properties.

Typical crown ethers suitable for the practice of this 7 invention are described in SClENCE, Volume 174, No.

4,008, Oct. 29, 1971, Pages 459-467 and Angew, Catm. International Addition, Volume 1, 1972, No. 1, Pages 16-25. While some of the structures and descriptions will be included herein, the details and scope of the disclosures of structures in compounds of these two articles are incorporated herein by reference.

The macrocyclic polyethers (crown compounds") can be assigned unique but very cumbersome names by application of the lUPAC rules for bridged hydrocarbons (rules A-31 and A-32). The rules for fused polycyclic compounds (A2l to A-23) likewise give un equivocal but most complicated names. A system of names was therefore devised solely for the ready identification of these compounds. The examples below illustrate how these names are made up of the side-ring substituents, the total number of atoms inthe polyether ring, the crown, and the number of oxygen atoms in the main ring. The crown names are simple but should only be used in conjunction with formulas since they are not unambiguous. Cyclohexane rings fused to the polyether ring as in compound! (30) may be termed perhydrobenzene but more commonly are called cyclohexyl.

Typical crown ethers that can be used as catalyst components in the process of this invention include those represented by the following structural formulas and identified by their specific crown" names:

Dibenz0l141crowr1-4 Benzoperhydrobenzo[ l8 lcrown-6 Perhydrodibenzol l8 ]crown-6 Dibenzol l8]crown6 Dibenzolll ]crown-7 Dibenzol24lcrown-8 Dibenzl301crown-l0 Dibenzol48lcrown-l6 DibenzolfiOlcrown-ZO TribenaollQlcrown-fi W Eetrabenzol241crown-8 Tn'benzol301crown-6 The aromatic crown polyethers are prepared by straight-forward condensation methods exemplified by the stoichiometric equations (1) to (3), in which 0 and T represent divalent organic groups generally of the formula -(CH CH2 )nCH2CH The condensations are typically run in 2-butanol under reflux for 12 to 24 hours. Method (1) can be used to prepare, for example, benzo[ l 2]crown-4 (yield 4 percent). Method (2) gives, for instance, dibenzo- [l8]crown-6. The starting material for method (3) is made by attaching a base-stable protecting group, e.g., benzyl or tetrahydropyranyl, to one of the hydroxyls of catechol; two moles of this compound are then condensed with Cl-Q-Cl, and the protecting group is subsequently removed. Eq. (3) is most convenient for synthesis of uneven-numbered polyether rings, e.g., dibenzo-[2l1crown-7.

Aromatic macrocyclic polyethers containing neutral substituents, such as alkyl or chloro. may be prepared by using suitable substituted aromatic vicinal diols. Of course, the substituentsmust be inert toward sodium hydroxide. and the open-chain dichloropolyether.

Saturated polyethers are prepared-from the corresponding aromatic ones by catalytic hydrogenation, typically in 2-butanol at 100 C.' and 7-10 atm. over a ruthenium catalyst. Recovery of the product is best done by column chromatography on alumina, and the yields are almost quantative.

Sodium and potassium alkyl compounds that can be used have l-10, preferably 3-8 carbon atoms and .include compounds in which the alkyl portion is methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, r-butyl, n-amyl, sec.-amyl, t-amyl, n-hexyl, sec.-hexyl, r-hexyl, n-octyl, l,l ,5-trimethyl-pentyl, n-decyl, l-methyl-2,4- diethyl-pentyl, etc. Even though larger groups can be used, there is no particular advantage, and the sodium or potassium can be attached to a primary, secondary or tertiary carbon atom.

These can be preparedby the reaction of metallic sodium or potassium with the corresponding halohydrocarbon. in cases where itis desired to prepare the sodium or potassium alkyl free of the byproduct. halide, this can be done by adding a solution of sodium or potassium alkoxide,such as NaOr-Buin cyclohexane, to a hexane solution of halide-free alkyl lithium. The resultant Na or K alkyl precipitates and, after filtering, the solid Na or K alkylis washed under nitrogen with hexane to remove any lithium residues.

In addition to monosodium:- or monopotassiumalkyl compounds, hydrocarbons havingltwo sodium or potassiumatoms attached can also beused, such asbutanel,4-disodium, pentane-l,4-disodium, butane-1,4- dipotassium, etc. These compounds are prepared by the same methods as described above for preparingthe monosodium of monopotassium compounds starting with dichlorohydrocarbon or dilithiohydrocarbon. However, these compounds are. not as practicalas the monosodium or monopotassium compounds and the latter are therefore preferred. Nevertheless, the use of the disodium anddipotassium hydrocarbon compounds are considered as coming within the scope of this invention.

Conjugated dienes that may be polymerized, either alone or with each other, in accordance with this invention include: l,3butadiene, isoprene, chloroprene, 2-phenyl-l ,S-butadiene, piperylene,.etc.

Although dienehomopolymers, or copolymers of two or more dienes, particularly butadiene homopolymers are preferred in the practice of this invention, diene copolymers can also be used wherethecomonomers impart desirable properties and do not detract from the diene polymer properties. The comonomers can be olefins, such as butene-l, n-butene-Z, isobutylene, npentene-l n-pentene-2 and thelike, and preferably are vinyl aryl or isopropenyl aryl compounds or derivatives thereof having alkyl, aralkyl, cycloalkyl or chlorine attached to the aromatic nucleus, and preferably having no more than carbon atoms. Typical of these aromatic comonomers arestyrene, alphamethyl styrene, vinyl toluene, isopropenyl toluene, ethyl styrene, pcyclohexyl styrene, o-, mand p Clstyrene, vinyl naphthalene, vinyl cyclohexyl naphthalene, vinyl methyl naphthalene, vinyl butyl naphthalene, isopropenyl naphthalene, isopropenyl isopropyl naphthalene, l-vinyl-4-chloronapthalene, l-isopropenyl5- chloronaphthalene, vinyl diphenyl, vinyl diphenylethane, 4-vinyl-4"methyldiphenyl, 4-vinyl-4'- chlorodiphenyl, and the like. Preferably such comonomers have no more than 12 carbon atoms. Where such comonomers are to be used, generally at least 1 percent, preferably at least 5 percent by weight should be used and as much as 60 percent, preferably no more than 30 percent may be used.

The polymerization is preferably effected in the presence of an inert diluent to facilitate handling of the polymer and to give better temperature control. Liquid hydrocarbons are preferred for this purpose, such as benzene, toluene, cyclohexane, saturated aliphatic hy drocarbons preferably of the straight chain variety, such as n-hexane, n-heptane, etc. The concentration of monomer is not critical, but for practical purposes it is generally in the range of 10-80 percent by weight.

Polymers produced according to this invention have molecular weights of 25,000 to l,000,000, generally l00,000 to 500,000. Yields of at least percent and as high as -99 percent are easily produced. The l,2configuration in the polymer is generally in the range of 65-85 percent, most often 70-75 percent. lt has been found that desirable wet traction or skid resistance properties result from such ranges of 1,2 configuration in the polymers.

The process should also be conducted under substantially anhydrous conditions. This is accomplished by using anhydrous reactants and dry reaction vessels and maintaining customary precautions during the reaction to keep moisture out of the reaction vessel. The reactants should also be free of impurities which react with the catalyst components. Such impurities may be tested for by titration with Michlers ketone according to procedures known in this art.

The process of this invention is advantageously con ducted in a closed system wherein the loss of solvent or monomer by evaporation is reduced or avoided in addition to which air and moisture are excluded. As a convenience, the pressureat which the reaction is conducted may be the pressure created by the system, i.e., autogenous pressure. If desired, however, higher or lower pressures may be employed.

At the completion of the reaction, the mixture is treated with a proton donor to deactivate the metal compound and the polymer recovered. This is preferably accomplished by adding the crude reaction mixture to a large amount of alcohol or water and then recoveringthe polymer coagulate. This procedure not only deactivates but also removes the metal compound from the polymer.

The dilute solution viscosity (DSV) referred to herein is defined as the inherent viscosity determined at 25 C. on a 0.4 percent solution of the polymer in toluene. It is calculated by dividing the natural logarithm of the relative viscosity by the present concentration of the solution, i.e., it is the inherent viscosity measured at 0.4 percent concentration. The molecular weights reported herein are determined from these viscosities. High resolution nuclear magnetic resonance (NMR) spectra of the conjugated diene polymers are used to determine the polymer microstructure.

Where normal precautions are taken to exclude im purities from the polymerization system which will adversely affect the catalyst, the polymerization will proceed without detectable chain termination. Therefore the molecular weight may be increased to any desired value within the range indicated above by the presence of sufficient monomer to give that molecular weight on the basis of moles of Na or K hydrocarbon, and the conversion can be carried out to any desired degree, even up to 100 percent, by continuing the reaction for boil by placing the bottle on a heated sand bath. When approximately 10 percent of the charge has been vented, the bottle is rapidly sealed. Such a procedure substantially excludes the air and oxygen which drastia sufficient period. Generally substantially complete cally inhibit polymerization. conversion can be obtained in less than 16 hours, and The sealed bottles may be placed on a polymerization in most cases less than 8 hours. For practical purposes wheel immersed in a liquid maintained at a constant it may be desirable to terminate the reaction prior to temperature, and rotated. Alternatively, the charge complete conversion, for example in the range of bottle may be allowed to stand stationary in a constant 75-95 percent and thereby for practical purposes retemperature bath, or otherwise heated or cooled, until duce the reaction period. the polymerization reaction is complete. Ordinarily, Although variations of temperature within the range the static system which requires a considerably longer indicated above will generally not affect the type of reaction, may in some instances be attractive where polymer produced, an increase in temperature does inhigher molecular weights are desired. After the induc crease the rate of polymerization. As stated above, the tion period, the charge goes through a period of thicktemperature range is advantageously 50l 50 C. and ening and finally becomes solid. At the end of the polypreferably 3080 C. At these temperatures, the reacmerization reaction, when properly conducted, all of tion is advantageously conducted for 2l6 hours and at the monomer has been consumed and there is a partial 6-8 hours in the preferred temperature range. vacuum in the free space of the reaction vessel. After it is essential that air be excluded during the prepara- 20 the polymerization has been completed, and the bottle tion of the potassium and sodium hydrocarbon compocooled to handling temperature, the polymer may be nents and that air is completely removed, if any is presremoved by cutting the bottle open. ent, from the crown ether before it is complexed with Small and large scale polymerizations can also be run the potassium or sodium hydrocarbon. Oxygen, nitroin stainless steel stirred reactors. gen and other components of the air seriously inhibit Corresponding techniques are employed in large the desired polymerization reaction and consequently scale polymerization processes. Usually the reaction should be excluded from the reaction zone. It is neceswill be carried out in a closed autoclave provid d i h sary that the catalyst be prepared in closed containers a heat transfer jacket and rotary agitator. Avoidance of provided with means for exclusion of air. Preferably, air contamination is most easily secured by evacuating the catalyst will be employed shortly after preparation, the vessel prior to charging the monomer and solvent although the catalyst may be stored for reasonable perid employing an inert atmosphere. To insure the pu ods of time if substantial contact with the atmosphere rity of the mon mer nd lvent, a ili l or h r is prevented during storage and during subsequent insuitable adsorption column is preferably inserted in the troduction into the reaction chamber. The catalyst may charging line employed for introduction of these matebe produced in situ in the reaction vessel. rials to the reactor. The catalyst is preferably charged Since moisture tends to use up catalyst, it should also last, conveniently from an auxiliary charging vessel be excluded from the reaction zone insofar as is possipressured with an inert gas and communicating with laboratory or Small Scale equipment, all of these the polymerization vessel through a valved conduit. It Substances Conveniently y be removed y bringing is desirable to provide a reflux condenser to assist in'the the polymerization charge to a boil and venting a small 40 l ion of the reaction temperature. pr p r i n of the Charge -g about 10 P Prior ln referring herein to monomer composition it is to introducing the catalyst to the reactor and effecting i t d d to m an the monomer portion of the polymerp lymerizati n- In rg scale pr however. ization solution, that is, the conjugated diene plus any charging of the reactor is preferably conducted under n mer that may be present. an inert atmosphere. Various methods of practicing the invention are illus- Laboratory Scale polymerization reaction m y C trated by the following examples. These examples are veniently be conducted in glass beverage bottles sealed intended merely to illustrate the invention and not in with aluminum lined crown caps. The polymerization any sense to limit the manner in which the invention bottles should be carefully cleaned and dried before can be practiced. The parts and percentages recited use. The catalyst employed may be added to the bottle therein and all through the specification, unless specifiby weight, or, where possible, the catalyst can be cally provided otherwise, are by weight. melted and added by volume. in some instances, it is desirable to add the catal st as a sus ension in the monomer or solvent. The inonomer is added by vol EXAMPLE I ume, desirably employing sufficient excess so that A series of polymerizations are conducted in 28 about 10 percent of the charge can be vented to reounce sealed bottles as described above using the catamove moisture, oxygen and air from the bottle. The relyst (nBuNa/bicyclohexyH 8-crown-l 6) charges indi moval of oxygen from the free air space above the cated below.The polymerization is conducted at 30C. monomer in the polymerization bottle as well as disfor 32 hours with the monomer added as 23 percent sosolved oxygen in the monomer is an important step in lution in hexane, the crown ether as a 0.052 mole/liter the bottle loading procedure. The cap is placed loosely solution in hexane, and the nBuNa as a 0.66 mole/liter on the bottle and the monomer is brought to a vigorous solution in mM mM nBuNa/ Gms. mMoles Ratio Exp. of Crown mMolcs nBuNa/ Gms. "/1 ldent. BD Ether nBuNa Ether Mon. Conv. DSV

A 60.3 0.204 1.65 8/1 2.74 76.3 2.89 B 58.9 0.260 1.65 6.35/1 2.80 91.7 3.72 C 60.3 0.31 1.65 5.3/1 2.74 94.5 5.20 D 54.3 0.36 1.65 4.6/1 3.04 33.7 3.77

EXAMPLE 11 The procedure of Example 1 is repeated a number of times to produce polymers similar to those of Example 1 using tricyclohexyl-18-crown-6 as the crown ether. The polymerizations are conducted for 3 days at 30 C. using the following proportions mM mM nBuNa/ Gms. mMoles Ratio 100 Exp. of Crown mMoles nBuNa/ Gms. 7: ldent. BD Ether nBuNa Ether Mon. Conv.

A I 36.8 0.146 248 17/1 6.74 B 37.0 0.366 3.30 9/1 8.92 41 C 37.4 1.168 4.95 4.2/1 13.23 60.4

The polymers have good processibility and have good properties similar to those of Example 1.

EXAMPLE Ill The polymers have properties similar to those of Exam ple l. The conversion in Run A is only about 45 percent whereas in Runs B-E it is 70-90 percent.

EXAMPLE V The procedure of Example I is repeated 21 number of times using a mixture of butadiene and styrene, tricyclohexyl-18-crown-6 and the proportions shown below.

mM Gms. mM nBuNa/ Gms. of mM Ratio 100 Exp. of Sty Crown mM nBuNa/ Gms. ldent. BD rene Ether nBuNa Ether Mon.

A 59.8 9 0.06 1.6.5 27.5/1 2.40 B 56.8 9 0.146 1.6.5 11.3/1 2.50 C 61.6 9 0.292 3.30 11.3/1 4.67 D 58 2 9 0.584 1.65 2.8/1 2.46 20 The polymers have properties similar to those of Example 1.

EXAMPLE V1 The procedure of Example I is repeated a number of times using a variety of temperatures with an 80/20 mixture of butadiene and styrene (in hexane) and tricyclohexyl-l8-crown-6 (with nBuNa) as reported The procedure of Example I is repeated using isobelow: prene as the monomer (in a 17 percent solution with O f M 11M gnrl I ms. 0 m 11110 1'] U 21 hexane) and usmg tr1cyclohexyl-l8-crown6 as the Exp BD/ Crown mM Bum, m0 Gms Temp crown ether. ldent. Styrene Ether nBuNa Ether Monomer C.

A 62 0.117 2.97 25.4/1 4.79 5 B 16. 0.146 3.30 226/1 5.32 5 C d0. 0.117 2.97 25.4/1 4.79 30 D do. 0.146 1.65 10.6/1 2.66 30 0198- mM R9119 mM nBuNfl/ E d0. 0.117 2.97 25.4/1 4.79 50 Exp. of Crown mM nBuNa/ 100 Gms. F ClO. 0.146 3.30 22.6/1 5.32 50 ldent. lso- Ether nBuNa/ Ether Monomer G d 0117 L32 I 13/1 2.13 80 Prene 11 d0. 0.146 1.65 10.6/1 2.66 110 A 47.3 0.059 1.65 28/1 3.49 40 B 411.5 0.146 1.65 11.3/1 3.40 I y C 4444 0-293 I1425/1 The polymers have properties s1m111ar to those of Exam- D 48.6 0.585 3.30 564/] 6.77

An analysis of the polymer from Exp. B shows 56.5 percent 3,4; 23 percent 1,4-trans; 11.8 percent cis and 8.7 percent 1,2 configuration. The molecular weights are in the same range as for Example I and the polymers have good processibility as well as wearability and wet traction in tire compositions.

EXAMPLE IV The procedure of Example 1 is repeated a number of times using the same crown ether and conditions of Ex ample 1 with the proportions and conditions shown below.

ple 1.

EXAMPLE VII The procedure of Example 1 is repeated a number of times using an 80/20 mixture of butadiene and styrene as a 20 percent solution in hexane. The crown ether is tricyclohexy118-crown-6 and the temperature is 30 C.

The polymers have properties similar to those of the polymers of Example 1.

EXAMPLE VIII The procedure of Example I is repeated except that a 2-gallon stainless steel-lined reactor is used equipped with stirrer, temperature control and recording means and inlet and outlet. To this reactor there is introduced a 23 percent butadiene in hexane solution containing 981 gms. of butadiene. Also added are 145 gms. of styrene, 2.34 millimoles of tricyclohexyl-l8-crown-6 and 26.4 millimoles of nBuNa. The reaction mixture is stirred and maintained at 86 F. (30 C.) for a prolonged period with samples removed periodically for determination of percent of conversion. At the end of 25 hours, there is 32.4 percent conversion; after 49 hours, there is 43.4 percent conversion; and at 113 10 hours, there is 51 percent conversion. The reagents used represent a nBuNa/crown ether ratio of 11.28/1 and 2.34 millimoles of nBuNa per 100 grams of monomer. The polymer has properties similar to those of the polymers of Example 1.

EXAMPLE IX The procedure of Example V111 is repeated, omitting the styrene and using 1148 gms. of butadiene, 2.41 miltimes using n-Butyl K and tribenzo-18-crown-6 as the catalyst combination for 52 hours at 30 C.

The polymers have properties similar to those of Example I.

EXAMPLE XIV The procedure of Example 1 is repeated a number of limoles of tricyclohexyl18-erown-6, 27.2 millimoles of 20 times using lsohexyl K and dlbenZ014'CmWn4 as the nBuNa and a reaction period of 2 days. These amounts represent a nBuNa/crown ether ratio of 11.28/1, and 2.37 millimoles of nBuNa per 100 gms. of monomer. The product has a Mooney viscosity of 83 (ML/4) and other properties similar to those of the polymers of Example 1.

EXAMPLE X The procedure of Example V111 is repeated, using a mixture of 843.8 gms. of butadiene and 233.9 grams of isoprene in approximately 21 percent hexane solution, 2.41 millimoles of tricyclohexyl-l8-crown-6 and 27.19 millimoles of nBuNa. These amounts represent a nBu- Na/crown ether ratio of l 1.28/1, and 2.58 millimoles of catalyst combination for 72 hours at 30 C.

The procedure of Example 1 is repeated a number of nBuNa per 100 gms. of monomer. The polymerization times using t'amyl K and trlbenzo'ls'cmwn'fi the is conducted for 43 hours and gives a 50 percent yield of a copolymer having a dilute solution viscosity of 2.04.

EXAMPLE XI The procedure of Example I is repeated a number of times using n-amyl Na and dibenzo-14-crown-4 as the catalyst combination at 30 C. for 48 hours.

The polymers are similar in properties to those of Example 1.

EXAMPLE X11 The procedure of Example 1 is repeated a number of times using 2-ethylhexy1 Na and dibenzo-2l-crown-7 as the catalyst combination at 30 C. for 50 hours.

mM Gms. mM mM Ratio mM/Na Exp. of Crown Z-Ethyl- N21! 100 gms. ldent. BD Ether Hexyl Na Ether Monomer DSV A 58.9 0.23 1.67 7.26/1 2.84 2.45 B 60.2 0.26 1.67 6.42/1 2.77 3.18 C 59.6 0.34 1.67 4.9/1 2.8 4.74

catalyst combination for 64 hours at 30 C.

mM mM Gms. mM mM Ratio t-Am K/ Exp. of Crown t-Amyl t-Amk/ Gms. ldent. BD Ether K Ether Monomer DSV A 60.2 0.24 1.66 7/1 2.76 2.18 B 60.4 0.27 1.66 6/1 2.75 3.76 C 58.9 0.36 1.66 4.6/1 2.82 5.12

While certain features of this invention have been described in detail with respect to various embodiments thereof, it will, of course, be apparent that other modifications can be made within the spirit and scope of this invention and it is not intended to limit the invention to the exact details shown above except insofar as they are defined in the following claims:

The invention claimed is:

l. A process for the hydrocarbon solution polymerization of a monomer composition containing at least 70 percent conjugated diene comprising the step of maintaining said monomer composition at a temperature of 50 to C in intimate contact with a catalyst composition consisting essentially of:

a. a sodium or potassium alkyl having 1-10 carbon atoms; and

b. a crown ether consisting essentially of a heterocyclic structure of at least 3 oxygen atoms and aliphatic or aromatic hydrocarbon radicals, adjacent oxygen atoms in said heterocyclic structure being separated from and joined to each other by at least two carbon atoms of said hydrocarbon radicals and, where cycloaliphatic or aromatic rings are being present in said catalyst composition in a ratio of 0.0ll.0 mole per mole of sodium or potassium alkyl, said polymerization being conducted for a period of at least 2 hours.

2. The process of claim 1 in which the heterocyclic structure in said crown ether has at least 4 oxygen atoms and at least 8 carbon atoms therein.

3. The process of claim 2 in which said temperature is 50-80 C.

4. The process of claim 3 in which said conjugated diene is essentially all 1,3-butadiene.

5. The process of claim 3 in which said conjugated diene is 1,3-butadiene.

6. The process of claim 5 in which said polymerization is conducted for at least 6 hours.

7. The process of claim 6 in which said alkyl is a sodium alkyl, said catalyst composition contains 2-7 millimoles of sodium alkyl per 100 grams of monomer and 0.0l50.5 millimoles of crown ether per millimole of sodium alkyl. j j

8. The process of claim 7 in which said crown ether is bicyclohexyl-l 8-crown-6.

9. The process of claim 7 in which said crown ether is tricyclohexyll 8-crown-6.

10. The process of claim 7 in which said crown ether is dibenzo-l4-crown-6. 7

11. The process of claim 7 in which said crown ether is dibenzo-l 8-crown-6.

12. The process of claim 7 in which said crown ether is tribenzo-l8-crown-6.

13. The process of claim 7 in which said sodium alkyl is n-butyl sodium.

14. The process of claim 7 in which said sodium alkyl is n-butyl sodium.

15. The process of claim 14 in which said hydrocarbon solution is hexane.

16. The process of claim 1 in which said alkyl is nbutyl sodium.

solution is hexane. 

2. The process of claim 1 in which the heterocyclic structure in said crown ether has at least 4 oxygen atoms and at least 8 carbon atoms therein.
 3. The process of claim 2 in which said temperature is 50*-80* C.
 4. The process of claim 3 in which said conjugated diene is essentially all 1,3-butadiene.
 5. The process of claim 3 in which said conjugated diene is 1,3-butadiene.
 6. The process of claim 5 in which said polymerization is conducted for at least 6 hours.
 7. The process of claim 6 in which said alkyl is a sodium alkyl, said catalyst composition contains 2-7 millimoles of sodium alkyl per 100 grams of monomer and 0.015-0.5 millimoles of crown ether per millimole of sodium alkyl.
 8. The process of claim 7 in which said crown ether is bicyclohexyl-18-crown-6.
 9. The process of claim 7 in which said crown ether is tricyclohexyl-18-crown-6.
 10. The process of claim 7 in which said crown ether is dibenzo-14-crown-6.
 11. The process of claim 7 in which said crown ether is dibenzo-18-crown-6.
 12. The process of claim 7 in which said crown ether is tribenzo-18-crown-6.
 13. The process of claim 7 in which said sodium alkyl is n-butyl sodium.
 14. The process of claim 7 in which said sodium alkyl is n-butyl sodium.
 15. The process of claim 14 in which said hydrocarbon solution is hexane.
 16. The process of claim 1 in which said alkyl is n-butyl sodium.
 17. The process of claim 1 in which said hydrocarbon solution is hexane. 